1. Field of the Invention
The present invention relates to disk drives. More particularly, the present invention relates to a disk drive that provides for internal disk drive temperature estimation.
2. Description of the Prior Art and Related Information
Today, computers are routinely used both at work and in the home. Computers advantageously enable file sharing, the creation of electronic documents, the use of application specific software, and electronic commerce through Internet and other computer networks. Typically, each computer has a storage peripheral such as a disk drive (e.g. a hard disk drive).
A huge market exists for hard disk drives for mass-market computer systems such as servers, desktop computers, and laptop computers. To be competitive in this market, a hard disk drive should be relatively inexpensive and embody a design that is adapted for low-cost mass production.
Typically, the main assemblies of a hard disk drive are a head disk assembly (HDA) and a printed circuit board assembly (PCBA). The head disk assembly includes an enclosure including a base and a cover, at least one disk having at least one recording surface, a spindle motor for causing each disk to rotate, and an actuator arrangement. The PCBA generally includes circuitry for processing signals and controlling operations in the disk drive.
An actuator arrangement that is commonly used in hard disk drives is a rotary actuator arrangement included as part of a head stack assembly (HSA) that includes a collection of elements of the head disk assembly. The collection typically includes certain prefabricated subassemblies and certain components that are incorporated into the head disk assembly. For example, a prefabricated head stack assembly (HSA) may include a pivot bearing cartridge, a rotary actuator arrangement, and permanent magnets and an arrangement for supporting the magnets to produce a magnetic field for a voice coil motor (VCM).
The rotary actuator arrangement of the HSA may also include a coil forming another part of the VCM, an actuator body having a bore through it, and a plurality of arms projecting parallel to each other and perpendicular to the access of the bore. The rotary actuator arrangement of the HSA may also include head gimbal assemblies (HGAs) that are supported by the arms. Each HGA includes a load beam and a head supported by the load beam. The head is positioned over a track on a recording surface of the disk to write or read data to or from the track, respectively.
Typically, the body portion and the arms of the HSA are made out of metal and form a unitary structure known as an “E block.” The E block may include any number of arms, e.g., one, two, three, four, five, six, etc. However, these types of HSAs tend to have a relatively high mass since the entire unitary structure of the E block is typically made out of metal. This relatively high mass results in a corresponding high moment of inertia about the pivot axis of the HSA. Because of this high moment of inertia, in order to pivot the head of the HSA to access data from the disk, a relatively large amount of power needs to be applied to the coil of the VCM.
During operation of the disk drive, it is useful to determine the internal ambient disk drive temperature. One way of achieving this is by utilizing a heat sensing device located within the disk drive. Unfortunately, the use of an extra heat sensing device adds significant cost to the disk drive.
Other attempts have been made to estimate the internal ambient temperature of the disk drive based upon measuring pre-existing signals of the disk drive. One way that this has been done is by calculating a junction temperature (JTemp) based upon a breakthrough voltage of the preamplifier of the HSA. In effect, this measurement is accomplished by utilizing a temperature characterization of the PN junction of the preamplifier to simulate temperature measurement. Unfortunately, this technique is very inaccurate. For example, the estimated internal ambient disk drive temperature value may be significantly off from the actual internal ambient disk drive temperature.
One particular problem with this type of estimation is that it does not take into account the additional heat that is imparted to the preamplifier as a result of the VCM moving the HSA by powering the coil. This in turn heats the E block and other components of the disk drive, and particularly imparts heat to the preamplifier, whereas the actual internal ambient disk drive temperature is not raised that significantly. Thus, current techniques do not take into account the added temperature noise resulting from the use of a VCM.